graph for projectile... (2 Viewers)

[spyder]

hey
doesnt the graph increase at a decreasing rate
we're graphing horizontal velocity vs range here
as the initial horizontal velocity increases, it will move off the table at a greater speed but u gotta also take into account g
which acts to pull it down
the longer it is in the air, the larger the effect of g
meaning that yeh the range increases with increased horizontal velocity, but at a decreasing rate coz g has more of an effect on the ball, pulling it down more n therefore decreasing the range

s = ut yeh
but t doesnt remain constant
so how can the graph be linear?
t changes with u

wat do uze think?
it makes sense to me

 

[walla]

nah spyder its in the air the same amount of time for each test
vertical motion is unaffected by changes in horizontal speed

 

[spyder]

ah fuk ur rite
hahah

 

[william]

the horizontal speed should be the gradient that is 1.85. but when I subs that two values in, it comes out another value 1.9 something

 

[worlds greatest]

how convenient that takuya doesnt reply when he realises he got pwned

(see "how do u think u went" poll/thread)
(im not sure if thats the exact name)

 

[~TeLEpAtHeTiC~]

lol so true
this question i rekon i fucked up... over all exam was good..but i didn't like this question..was never good with projectile motion
but my graph is thesame as all u are saying..so i assume i'm right..OR..were ALL wrong
lol
good luck everyone

 

[juber]

Did everyone remember to put their independant variable on the horizontal axis?

I.e. indpendant variable = velocity
dependant variable = range

Also, I dont know if we needed to put a scale on the graph because it said that we need only show the relationship. I think that as far as a scales concerned, as long as you appropriately extrapolated the first example (and put the correct figues on the side) then youd be pretty right...

But what does everyone think about a scale?

 

[walla]

scale doesn't hurt but yeah if you identified 0,0 and the point from the first test it would be right

 

[tegs]

yeah, the speed was 1.85m/s, and the graph should have just been through (0,0) and (0.6, 1.85) as a straight line, which demonstrates that the faster it's going, the further it will go.

 

[<METALHEAD>]

The thing that pissed me off about this question was that the graph from the data logger was actually impossible, in no position could the data logger have recorded thos figures. But i got the same graph as the rest of you, by assumption.

 

[Bannanafish]

why is it impossible??

 

[<METALHEAD>]

I attempted to work out the distances. They didnt work. + there is no way that a linear graph for distance to time can represent an increasing net velocity (static horizontal velocity (assumed in physics) + increasing vertical velocity due to gravity)

 

[Bannanafish]

er the thing only measures horizontal displacement, hence horizontal velocity

also if you looked, it stoped giving out figures after the ball went off the ledge

 

[<METALHEAD>]

Ummm, actually, it started when the ball went off the ledge, by my reading, and i dont recall it saying that it was only reading horizontal displacement, though i will admit i could be wrong there. I dont remember it that precisely.

 

[Bannanafish]

i think it was reading while it was on the ledge only
you can't measure velocity, you need to measure displacement and time (which is what the graph was) to calculate velocity

 

[<METALHEAD>]

Ummm, what i was saying was (and if youre right about it being on the ledge, it is irrelevant) That a displacement against time graph for a changing velocity (accelerated by gravity) is NOT A STRAIGHT LINE, which the graph given was.

 

[walla]

buddy it wasn't a displacement against time
it was a range against speed

 

[walla]

buddy it wasn't a displacement against time
it was a range against speed that we drew

oh and the graph they showed us was not an accelerated object...it was the displacement of the ball before it left the ledge, so no acceleration (ignoring friction)

 

[<METALHEAD>]

I wasn't talking about the graph drawn, i know what i drew. And ok, if the graph given was before it left the edge, then as i said above, irrelevant.

 

[helper]

The datalogger graph was for the ball was on the table. It was for displacements 0.5 to 1.5m. This was when it was on the table. There was no readings for after it left the table.

As such it was measuring the horizontal velocity, as no acceleration while on the table.

Misleading use of the datalogger, as it wasn't studying all the projectiles motion. Rather while it was on the table. It couldn't measure the whole horizontal motion, which the question implied but the graph contradicted.

Even if it was follwing the whole motion it still would have been a straight line as it was measuring the horizontal motion only.